The present invention relates to a method for increasing hydrophilicity of a fabric material. More particularly, the invention relates to a method for imparting a durably increased capacity of water absorption and a durably decreased susceptibility to accumulation of static electricity.
Needless to say, fabric materials currently on use both in the clothing use of people and in the industrial applications are in a very large part produced of synthetic fibers or traditional natural fibers. One of the largest differences between the properties of the synthetic and natural fibers is in the hydrophilicity-hydrophobicity behavior of them, the former fibers being of course outstandingly less hydrophilic than the latter. The remarkably small hydrophilicity of synthetic fibers sometimes causes serious problems not encountered in the use of natural fibers.
For example, fabric materials made of synthetic fibers have a very poor capacity of water or sweat absorption, which is advantageous on one hand but disadvantageous on the other, so that wearers of clothes made of synthetic fibers unavoidably have an unpleasant feeling of heavy stuffiness especially when the clothes are underwears worn in contact with or in the proximity of the skin of the wearer in a hot and humid climate.
Another serious problem caused by the poor hydrophilicity of synthetic fibers is the great accumulation of static electricity on the fibers causing unpleasantness to the wearer of clothes of synthetic fibers in such a charged condition.
Many attempts have of course been proposed and practiced in the prior art to solve these problems by increasing the hydrophilicity of the fabric materials of synthetic fibers and also natural fibres. For example, the problem of poor water absorption of synthetic fibers can be mitigated by the mixed spinning or mixed weaving with water-absorptive natural fibers. The effectiveness of this method is, however, limited since too much amounts of the natural fibers mixed with the synthetic fibers to attain sufficient hydrophilicity of the fabric material naturally result in the loss of the advantages inherent to synthetic fibers. An alternative method is the treatment of the fabric material of synthetic fibers with a water-absorbent agent-to impart hydrophilicity to the surface of the fibers. Extensive investigations have been and are being undertaken in this direction to propose various kinds of water-absorbent agents effective for a particular type of synthetic fibers. For example, the capacity of water absorption of polyester fibers, e.g. polyethylene terephthalate fibers, can be increased by the treatment with a water-soluble polyester resin. Unfortunately, such a method of the treatment of synthetic fibers with a water-soluble resin is defective in several respects of the poor durability of the effects obtained therewith and the adverse influences on the color fastness of dyed fabric materials in many cases.
Limiting the matter to the antistatic treatment or decrease of accumulation of static electricity on the synthetic fibers, various antistatic agents have been proposed hitherto. For example, the above mentioned water-soluble resins including water-soluble polyester resins, polyurethane resins, polyacrylamide resins, polyamide resins and the like are of course effective as an antistatic agent with certain durability. Besides, many compounds are known to be effective as an antistatic agent including inorganic salts such as calcium chloride and lithium chloride, guanidine compounds such as guanidine hydrochloride, surface active agents such as those of the types of quaternary ammonium salts and phosphoric acid esters, acrylic polymers having quaternary cationic groups and the like although the effectiveness of the treatment with these compounds is rather temporary.
The durability of the effects obtained with the above described antistatic agents is, however, not quite satisfactory even with the relatively durable polymeric antistatic agents and the antistatic effects obtained therewith are decreased in the long-run use of the treated fabric materials even by setting aside the other problem of the insufficient effectiveness of the method. Furthermore, the method is also not free from the problem of the decreased color fastness of dyed fabric materials giving limitations to the amount and the manner of use of the antistatic agents.
In short, none of the prior art methods by use of a hydrophilic agent, i.e. water-absorbent agent or antistatic agent, is quite satisfactory for imparting hydrophilicity to the fabric materials in respects of the effectiveness and the durability.
As given above one component of the compositions of the present invention are polyorganosiloxanes. Such compounds are known to be used on an industrial scale to finish fabrics by providing them with a permanent or semi-permanent finish aimed at improving their general appearance. Significant for these industrial fabric finishing processes is a co-called curing step generally involving temperatures in excess of 150° C. often for periods of one hour or more. The object here is to form a chemical finish which resists destruction during subsequent cleaning/laundering of fabrics. This process of finishing is not carried out in domestic applications and accordingly one would not expect benefits of a comparable nature or magnitude from polyorganosiloxanes included as adjuncts in domestic softeners. Indeed, it is noteworthy that if the compounds of the current invention achieved a permanence associated with industrial textile finishing, problems associated with a cumulative build through the wash cycles could occur such as fabric discoloration and even in extremes an unpleasant feel to the wearer.
Surprisingly, it has been found that the use of selected polyorganosiloxanes, or mixtures thereof, and selected additives in fabric softener compositions provide excellent hydrophilic effects when applied to fabrics during a textile laundry operation.
Similar benefits are noted when compositions of the current invention are incorporated into tumble dryer additives such as impregnates on sheets.